base/values.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // This file specifies a recursive data storage class called Value intended for
   6 // storing settings and other persistable data.
   7 //
   8 // A Value represents something that can be stored in JSON or passed to/from
   9 // JavaScript. As such, it is NOT a generalized variant type, since only the
  10 // types supported by JavaScript/JSON are supported.
  11 //
  12 // IN PARTICULAR this means that there is no support for int64 or unsigned
  13 // numbers. Writing JSON with such types would violate the spec. If you need
  14 // something like this, either use a double or make a string value containing
  15 // the number you want.
  16
  17 #ifndef BASE_VALUES_H_
  18 #define BASE_VALUES_H_
  19
  20 #include <stddef.h>
  21
  22 #include <iosfwd>
  23 #include <map>
  24 #include <string>
  25 #include <utility>
  26 #include <vector>
  27
  28 #include "base/base_export.h"
  29 #include "base/basictypes.h"
  30 #include "base/compiler_specific.h"
  31 #include "base/memory/scoped_ptr.h"
  32 #include "base/strings/string16.h"
  33
  34 // This file declares "using base::Value", etc. at the bottom, so that
  35 // current code can use these classes without the base namespace. In
  36 // new code, please always use base::Value, etc. or add your own
  37 // "using" declaration.
  38 // http://crbug.com/88666
  39 namespace base {
  40
  41 class DictionaryValue;
  42 class FundamentalValue;
  43 class ListValue;
  44 class StringValue;
  45 class Value;
  46
  47 typedef std::vector<Value*> ValueVector;
  48 typedef std::map<std::string, Value*> ValueMap;
  49
  50 // The Value class is the base class for Values. A Value can be instantiated
  51 // via the Create*Value() factory methods, or by directly creating instances of
  52 // the subclasses.
  53 //
  54 // See the file-level comment above for more information.
  55 class BASE_EXPORT Value {
  56  public:
  57   enum Type {
  58     TYPE_NULL = 0,
  59     TYPE_BOOLEAN,
  60     TYPE_INTEGER,
  61     TYPE_DOUBLE,
  62     TYPE_STRING,
  63     TYPE_BINARY,
  64     TYPE_DICTIONARY,
  65     TYPE_LIST
  66     // Note: Do not add more types. See the file-level comment above for why.
  67   };
  68
  69   virtual ~Value();
  70
  71   static Value* CreateNullValue();
  72   // DEPRECATED: Do not use the following 5 functions. Instead, use
  73   // new FundamentalValue or new StringValue.
  74   static FundamentalValue* CreateBooleanValue(bool in_value);
  75   static FundamentalValue* CreateIntegerValue(int in_value);
  76   static FundamentalValue* CreateDoubleValue(double in_value);
  77   static StringValue* CreateStringValue(const std::string& in_value);
  78   static StringValue* CreateStringValue(const string16& in_value);
  79
  80   // Returns the type of the value stored by the current Value object.
  81   // Each type will be implemented by only one subclass of Value, so it's
  82   // safe to use the Type to determine whether you can cast from
  83   // Value* to (Implementing Class)*.  Also, a Value object never changes
  84   // its type after construction.
  85   Type GetType() const { return type_; }
  86
  87   // Returns true if the current object represents a given type.
  88   bool IsType(Type type) const { return type == type_; }
  89
  90   // These methods allow the convenient retrieval of the contents of the Value.
  91   // If the current object can be converted into the given type, the value is
  92   // returned through the |out_value| parameter and true is returned;
  93   // otherwise, false is returned and |out_value| is unchanged.
  94   virtual bool GetAsBoolean(bool* out_value) const;
  95   virtual bool GetAsInteger(int* out_value) const;
  96   virtual bool GetAsDouble(double* out_value) const;
  97   virtual bool GetAsString(std::string* out_value) const;
  98   virtual bool GetAsString(string16* out_value) const;
  99   virtual bool GetAsList(ListValue** out_value);
 100   virtual bool GetAsList(const ListValue** out_value) const;
 101   virtual bool GetAsDictionary(DictionaryValue** out_value);
 102   virtual bool GetAsDictionary(const DictionaryValue** out_value) const;
 103   // Note: Do not add more types. See the file-level comment above for why.
 104
 105   // This creates a deep copy of the entire Value tree, and returns a pointer
 106   // to the copy.  The caller gets ownership of the copy, of course.
 107   //
 108   // Subclasses return their own type directly in their overrides;
 109   // this works because C++ supports covariant return types.
 110   virtual Value* DeepCopy() const;
 111
 112   // Compares if two Value objects have equal contents.
 113   virtual bool Equals(const Value* other) const;
 114
 115   // Compares if two Value objects have equal contents. Can handle NULLs.
 116   // NULLs are considered equal but different from Value::CreateNullValue().
 117   static bool Equals(const Value* a, const Value* b);
 118
 119  protected:
 120   // These aren't safe for end-users, but they are useful for subclasses.
 121   explicit Value(Type type);
 122   Value(const Value& that);
 123   Value& operator=(const Value& that);
 124
 125  private:
 126   Type type_;
 127 };
 128
 129 // FundamentalValue represents the simple fundamental types of values.
 130 class BASE_EXPORT FundamentalValue : public Value {
 131  public:
 132   explicit FundamentalValue(bool in_value);
 133   explicit FundamentalValue(int in_value);
 134   explicit FundamentalValue(double in_value);
 135   virtual ~FundamentalValue();
 136
 137   // Overridden from Value:
 138   virtual bool GetAsBoolean(bool* out_value) const OVERRIDE;
 139   virtual bool GetAsInteger(int* out_value) const OVERRIDE;
 140   virtual bool GetAsDouble(double* out_value) const OVERRIDE;
 141   virtual FundamentalValue* DeepCopy() const OVERRIDE;
 142   virtual bool Equals(const Value* other) const OVERRIDE;
 143
 144  private:
 145   union {
 146     bool boolean_value_;
 147     int integer_value_;
 148     double double_value_;
 149   };
 150 };
 151
 152 class BASE_EXPORT StringValue : public Value {
 153  public:
 154   // Initializes a StringValue with a UTF-8 narrow character string.
 155   explicit StringValue(const std::string& in_value);
 156
 157   // Initializes a StringValue with a string16.
 158   explicit StringValue(const string16& in_value);
 159
 160   virtual ~StringValue();
 161
 162   // Overridden from Value:
 163   virtual bool GetAsString(std::string* out_value) const OVERRIDE;
 164   virtual bool GetAsString(string16* out_value) const OVERRIDE;
 165   virtual StringValue* DeepCopy() const OVERRIDE;
 166   virtual bool Equals(const Value* other) const OVERRIDE;
 167
 168  private:
 169   std::string value_;
 170 };
 171
 172 class BASE_EXPORT BinaryValue: public Value {
 173  public:
 174   // Creates a BinaryValue with a null buffer and size of 0.
 175   BinaryValue();
 176
 177   // Creates a BinaryValue, taking ownership of the bytes pointed to by
 178   // |buffer|.
 179   BinaryValue(scoped_ptr<char[]> buffer, size_t size);
 180
 181   virtual ~BinaryValue();
 182
 183   // For situations where you want to keep ownership of your buffer, this
 184   // factory method creates a new BinaryValue by copying the contents of the
 185   // buffer that's passed in.
 186   static BinaryValue* CreateWithCopiedBuffer(const char* buffer, size_t size);
 187
 188   size_t GetSize() const { return size_; }
 189
 190   // May return NULL.
 191   char* GetBuffer() { return buffer_.get(); }
 192   const char* GetBuffer() const { return buffer_.get(); }
 193
 194   // Overridden from Value:
 195   virtual BinaryValue* DeepCopy() const OVERRIDE;
 196   virtual bool Equals(const Value* other) const OVERRIDE;
 197
 198  private:
 199   scoped_ptr<char[]> buffer_;
 200   size_t size_;
 201
 202   DISALLOW_COPY_AND_ASSIGN(BinaryValue);
 203 };
 204
 205 // DictionaryValue provides a key-value dictionary with (optional) "path"
 206 // parsing for recursive access; see the comment at the top of the file. Keys
 207 // are |std::string|s and should be UTF-8 encoded.
 208 class BASE_EXPORT DictionaryValue : public Value {
 209  public:
 210   DictionaryValue();
 211   virtual ~DictionaryValue();
 212
 213   // Overridden from Value:
 214   virtual bool GetAsDictionary(DictionaryValue** out_value) OVERRIDE;
 215   virtual bool GetAsDictionary(
 216       const DictionaryValue** out_value) const OVERRIDE;
 217
 218   // Returns true if the current dictionary has a value for the given key.
 219   bool HasKey(const std::string& key) const;
 220
 221   // Returns the number of Values in this dictionary.
 222   size_t size() const { return dictionary_.size(); }
 223
 224   // Returns whether the dictionary is empty.
 225   bool empty() const { return dictionary_.empty(); }
 226
 227   // Clears any current contents of this dictionary.
 228   void Clear();
 229
 230   // Sets the Value associated with the given path starting from this object.
 231   // A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
 232   // into the next DictionaryValue down.  Obviously, "." can't be used
 233   // within a key, but there are no other restrictions on keys.
 234   // If the key at any step of the way doesn't exist, or exists but isn't
 235   // a DictionaryValue, a new DictionaryValue will be created and attached
 236   // to the path in that location.
 237   // Note that the dictionary takes ownership of the value referenced by
 238   // |in_value|, and therefore |in_value| must be non-NULL.
 239   void Set(const std::string& path, Value* in_value);
 240
 241   // Convenience forms of Set().  These methods will replace any existing
 242   // value at that path, even if it has a different type.
 243   void SetBoolean(const std::string& path, bool in_value);
 244   void SetInteger(const std::string& path, int in_value);
 245   void SetDouble(const std::string& path, double in_value);
 246   void SetString(const std::string& path, const std::string& in_value);
 247   void SetString(const std::string& path, const string16& in_value);
 248
 249   // Like Set(), but without special treatment of '.'.  This allows e.g. URLs to
 250   // be used as paths.
 251   void SetWithoutPathExpansion(const std::string& key, Value* in_value);
 252
 253   // Convenience forms of SetWithoutPathExpansion().
 254   void SetBooleanWithoutPathExpansion(const std::string& path, bool in_value);
 255   void SetIntegerWithoutPathExpansion(const std::string& path, int in_value);
 256   void SetDoubleWithoutPathExpansion(const std::string& path, double in_value);
 257   void SetStringWithoutPathExpansion(const std::string& path,
 258                                      const std::string& in_value);
 259   void SetStringWithoutPathExpansion(const std::string& path,
 260                                      const string16& in_value);
 261
 262   // Gets the Value associated with the given path starting from this object.
 263   // A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
 264   // into the next DictionaryValue down.  If the path can be resolved
 265   // successfully, the value for the last key in the path will be returned
 266   // through the |out_value| parameter, and the function will return true.
 267   // Otherwise, it will return false and |out_value| will be untouched.
 268   // Note that the dictionary always owns the value that's returned.
 269   bool Get(const std::string& path, const Value** out_value) const;
 270   bool Get(const std::string& path, Value** out_value);
 271
 272   // These are convenience forms of Get().  The value will be retrieved
 273   // and the return value will be true if the path is valid and the value at
 274   // the end of the path can be returned in the form specified.
 275   bool GetBoolean(const std::string& path, bool* out_value) const;
 276   bool GetInteger(const std::string& path, int* out_value) const;
 277   bool GetDouble(const std::string& path, double* out_value) const;
 278   bool GetString(const std::string& path, std::string* out_value) const;
 279   bool GetString(const std::string& path, string16* out_value) const;
 280   bool GetStringASCII(const std::string& path, std::string* out_value) const;
 281   bool GetBinary(const std::string& path, const BinaryValue** out_value) const;
 282   bool GetBinary(const std::string& path, BinaryValue** out_value);
 283   bool GetDictionary(const std::string& path,
 284                      const DictionaryValue** out_value) const;
 285   bool GetDictionary(const std::string& path, DictionaryValue** out_value);
 286   bool GetList(const std::string& path, const ListValue** out_value) const;
 287   bool GetList(const std::string& path, ListValue** out_value);
 288
 289   // Like Get(), but without special treatment of '.'.  This allows e.g. URLs to
 290   // be used as paths.
 291   bool GetWithoutPathExpansion(const std::string& key,
 292                                const Value** out_value) const;
 293   bool GetWithoutPathExpansion(const std::string& key, Value** out_value);
 294   bool GetBooleanWithoutPathExpansion(const std::string& key,
 295                                       bool* out_value) const;
 296   bool GetIntegerWithoutPathExpansion(const std::string& key,
 297                                       int* out_value) const;
 298   bool GetDoubleWithoutPathExpansion(const std::string& key,
 299                                      double* out_value) const;
 300   bool GetStringWithoutPathExpansion(const std::string& key,
 301                                      std::string* out_value) const;
 302   bool GetStringWithoutPathExpansion(const std::string& key,
 303                                      string16* out_value) const;
 304   bool GetDictionaryWithoutPathExpansion(
 305       const std::string& key,
 306       const DictionaryValue** out_value) const;
 307   bool GetDictionaryWithoutPathExpansion(const std::string& key,
 308                                          DictionaryValue** out_value);
 309   bool GetListWithoutPathExpansion(const std::string& key,
 310                                    const ListValue** out_value) const;
 311   bool GetListWithoutPathExpansion(const std::string& key,
 312                                    ListValue** out_value);
 313
 314   // Removes the Value with the specified path from this dictionary (or one
 315   // of its child dictionaries, if the path is more than just a local key).
 316   // If |out_value| is non-NULL, the removed Value will be passed out via
 317   // |out_value|.  If |out_value| is NULL, the removed value will be deleted.
 318   // This method returns true if |path| is a valid path; otherwise it will
 319   // return false and the DictionaryValue object will be unchanged.
 320   virtual bool Remove(const std::string& path, scoped_ptr<Value>* out_value);
 321
 322   // Like Remove(), but without special treatment of '.'.  This allows e.g. URLs
 323   // to be used as paths.
 324   virtual bool RemoveWithoutPathExpansion(const std::string& key,
 325                                           scoped_ptr<Value>* out_value);
 326
 327   // Makes a copy of |this| but doesn't include empty dictionaries and lists in
 328   // the copy.  This never returns NULL, even if |this| itself is empty.
 329   DictionaryValue* DeepCopyWithoutEmptyChildren() const;
 330
 331   // Merge |dictionary| into this dictionary. This is done recursively, i.e. any
 332   // sub-dictionaries will be merged as well. In case of key collisions, the
 333   // passed in dictionary takes precedence and data already present will be
 334   // replaced. Values within |dictionary| are deep-copied, so |dictionary| may
 335   // be freed any time after this call.
 336   void MergeDictionary(const DictionaryValue* dictionary);
 337
 338   // Swaps contents with the |other| dictionary.
 339   virtual void Swap(DictionaryValue* other);
 340
 341   // This class provides an iterator over both keys and values in the
 342   // dictionary.  It can't be used to modify the dictionary.
 343   class BASE_EXPORT Iterator {
 344    public:
 345     explicit Iterator(const DictionaryValue& target);
 346
 347     bool IsAtEnd() const { return it_ == target_.dictionary_.end(); }
 348     void Advance() { ++it_; }
 349
 350     const std::string& key() const { return it_->first; }
 351     const Value& value() const { return *it_->second; }
 352
 353    private:
 354     const DictionaryValue& target_;
 355     ValueMap::const_iterator it_;
 356   };
 357
 358   // Overridden from Value:
 359   virtual DictionaryValue* DeepCopy() const OVERRIDE;
 360   virtual bool Equals(const Value* other) const OVERRIDE;
 361
 362  private:
 363   ValueMap dictionary_;
 364
 365   DISALLOW_COPY_AND_ASSIGN(DictionaryValue);
 366 };
 367
 368 // This type of Value represents a list of other Value values.
 369 class BASE_EXPORT ListValue : public Value {
 370  public:
 371   typedef ValueVector::iterator iterator;
 372   typedef ValueVector::const_iterator const_iterator;
 373
 374   ListValue();
 375   virtual ~ListValue();
 376
 377   // Clears the contents of this ListValue
 378   void Clear();
 379
 380   // Returns the number of Values in this list.
 381   size_t GetSize() const { return list_.size(); }
 382
 383   // Returns whether the list is empty.
 384   bool empty() const { return list_.empty(); }
 385
 386   // Sets the list item at the given index to be the Value specified by
 387   // the value given.  If the index beyond the current end of the list, null
 388   // Values will be used to pad out the list.
 389   // Returns true if successful, or false if the index was negative or
 390   // the value is a null pointer.
 391   bool Set(size_t index, Value* in_value);
 392
 393   // Gets the Value at the given index.  Modifies |out_value| (and returns true)
 394   // only if the index falls within the current list range.
 395   // Note that the list always owns the Value passed out via |out_value|.
 396   bool Get(size_t index, const Value** out_value) const;
 397   bool Get(size_t index, Value** out_value);
 398
 399   // Convenience forms of Get().  Modifies |out_value| (and returns true)
 400   // only if the index is valid and the Value at that index can be returned
 401   // in the specified form.
 402   bool GetBoolean(size_t index, bool* out_value) const;
 403   bool GetInteger(size_t index, int* out_value) const;
 404   bool GetDouble(size_t index, double* out_value) const;
 405   bool GetString(size_t index, std::string* out_value) const;
 406   bool GetString(size_t index, string16* out_value) const;
 407   bool GetBinary(size_t index, const BinaryValue** out_value) const;
 408   bool GetBinary(size_t index, BinaryValue** out_value);
 409   bool GetDictionary(size_t index, const DictionaryValue** out_value) const;
 410   bool GetDictionary(size_t index, DictionaryValue** out_value);
 411   bool GetList(size_t index, const ListValue** out_value) const;
 412   bool GetList(size_t index, ListValue** out_value);
 413
 414   // Removes the Value with the specified index from this list.
 415   // If |out_value| is non-NULL, the removed Value AND ITS OWNERSHIP will be
 416   // passed out via |out_value|.  If |out_value| is NULL, the removed value will
 417   // be deleted.  This method returns true if |index| is valid; otherwise
 418   // it will return false and the ListValue object will be unchanged.
 419   virtual bool Remove(size_t index, scoped_ptr<Value>* out_value);
 420
 421   // Removes the first instance of |value| found in the list, if any, and
 422   // deletes it. |index| is the location where |value| was found. Returns false
 423   // if not found.
 424   bool Remove(const Value& value, size_t* index);
 425
 426   // Removes the element at |iter|. If |out_value| is NULL, the value will be
 427   // deleted, otherwise ownership of the value is passed back to the caller.
 428   // Returns an iterator pointing to the location of the element that
 429   // followed the erased element.
 430   iterator Erase(iterator iter, scoped_ptr<Value>* out_value);
 431
 432   // Appends a Value to the end of the list.
 433   void Append(Value* in_value);
 434
 435   // Convenience forms of Append.
 436   void AppendBoolean(bool in_value);
 437   void AppendInteger(int in_value);
 438   void AppendDouble(double in_value);
 439   void AppendString(const std::string& in_value);
 440   void AppendString(const string16& in_value);
 441   void AppendStrings(const std::vector<std::string>& in_values);
 442   void AppendStrings(const std::vector<string16>& in_values);
 443
 444   // Appends a Value if it's not already present. Takes ownership of the
 445   // |in_value|. Returns true if successful, or false if the value was already
 446   // present. If the value was already present the |in_value| is deleted.
 447   bool AppendIfNotPresent(Value* in_value);
 448
 449   // Insert a Value at index.
 450   // Returns true if successful, or false if the index was out of range.
 451   bool Insert(size_t index, Value* in_value);
 452
 453   // Searches for the first instance of |value| in the list using the Equals
 454   // method of the Value type.
 455   // Returns a const_iterator to the found item or to end() if none exists.
 456   const_iterator Find(const Value& value) const;
 457
 458   // Swaps contents with the |other| list.
 459   virtual void Swap(ListValue* other);
 460
 461   // Iteration.
 462   iterator begin() { return list_.begin(); }
 463   iterator end() { return list_.end(); }
 464
 465   const_iterator begin() const { return list_.begin(); }
 466   const_iterator end() const { return list_.end(); }
 467
 468   // Overridden from Value:
 469   virtual bool GetAsList(ListValue** out_value) OVERRIDE;
 470   virtual bool GetAsList(const ListValue** out_value) const OVERRIDE;
 471   virtual ListValue* DeepCopy() const OVERRIDE;
 472   virtual bool Equals(const Value* other) const OVERRIDE;
 473
 474  private:
 475   ValueVector list_;
 476
 477   DISALLOW_COPY_AND_ASSIGN(ListValue);
 478 };
 479
 480 // This interface is implemented by classes that know how to serialize and
 481 // deserialize Value objects.
 482 class BASE_EXPORT ValueSerializer {
 483  public:
 484   virtual ~ValueSerializer();
 485
 486   virtual bool Serialize(const Value& root) = 0;
 487
 488   // This method deserializes the subclass-specific format into a Value object.
 489   // If the return value is non-NULL, the caller takes ownership of returned
 490   // Value. If the return value is NULL, and if error_code is non-NULL,
 491   // error_code will be set with the underlying error.
 492   // If |error_message| is non-null, it will be filled in with a formatted
 493   // error message including the location of the error if appropriate.
 494   virtual Value* Deserialize(int* error_code, std::string* error_str) = 0;
 495 };
 496
 497 // Stream operator so Values can be used in assertion statements.  In order that
 498 // gtest uses this operator to print readable output on test failures, we must
 499 // override each specific type. Otherwise, the default template implementation
 500 // is preferred over an upcast.
 501 BASE_EXPORT std::ostream& operator<<(std::ostream& out, const Value& value);
 502
 503 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 504                                             const FundamentalValue& value) {
 505   return out << static_cast<const Value&>(value);
 506 }
 507
 508 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 509                                             const StringValue& value) {
 510   return out << static_cast<const Value&>(value);
 511 }
 512
 513 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 514                                             const DictionaryValue& value) {
 515   return out << static_cast<const Value&>(value);
 516 }
 517
 518 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 519                                             const ListValue& value) {
 520   return out << static_cast<const Value&>(value);
 521 }
 522
 523 }  // namespace base
 524
 525 // http://crbug.com/88666
 526 using base::DictionaryValue;
 527 using base::ListValue;
 528 using base::StringValue;
 529 using base::Value;
 530
 531 #endif  // BASE_VALUES_H_